Question: Fix Boundary conditions for wave equation

How do I create a wave in Maple such that the end which the wave hits of (fixed boundary condition) is formed of triangles rather than just a straight line. I have, 

with(plots):

animate(plot3d,[sin(Pi*(t-x))sin(Piy)Heaviside(t-x)-sin(Pi(t+x))sin(Piy)*Heaviside(t+x),x=0..4,y=0..1],t=-2*Pi..2*Pi);

Would I have to create a whole new formula or can I just add something to the code to give this different boundary? Or maybe I can use a different software other than maple, I just want to know which directions the waves will travel when they hit a ridged surface.

Say I wanted to create a five sides polygon, so the wave hits these two boundary conditions so i can see what happens next. (I added the two black lines in paint so it was easier to visualise)